Use of a platinum alloy for spark plug electrodes and for spark plug electrode end pieces

Abstract

The use of a platinum alloy as material for production of a spark plug electrode or spark plug electrode end piece, wherein the platinum alloy consists of platinum (Pt), 40 to 4700 ppm by weight of at least one alloy metal (M1) selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr), 0% to 60% by weight of at least one alloy metal (M2) selected from the group consisting of chromium (Cr), iron (Fe), gold (Au), iridium (Ir), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag), titanium (Ti) and tungsten (W), and 0 or >0 to <1000 ppm by weight of unavoidable impurities in the form of one or more elements other than platinum and the alloy metals (M1) and (M2).

Description

[0001] USE OF A PLATINUM ALLOY FOR SPARK PLUG ELECTRODES AND SPARK PLUG ELECTRODE END PIECES

[0002] The invention relates to the use of a platinum alloy for at least one electrode of a spark plug or for producing at least one electrode of a spark plug or for at least one spark plug electrode end piece of a spark plug or for producing at least one spark plug electrode end piece of a spark plug, i.e., an electrode end piece of at least one of the electrodes of a spark plug. The invention therefore also relates to the following products: a spark plug electrode made of the platinum alloy, a spark plug electrode end piece made of the platinum alloy, a spark plug comprising at least one electrode made of the platinum alloy, and a spark plug comprising at least one electrode end piece made of the platinum alloy.

[0003] Spark plugs, as commonly used in internal combustion engines (piston engines, Wankel engines, turbines), have at least one ground electrode and at least one center electrode, between whose electrode ends or electrode end pieces the ignition sparks are generated during engine operation. State-of-the-art so-called platinum spark plugs, i.e., spark plugs with platinum electrodes or platinum electrode end pieces, are characterized by a significantly longer service life than those with non-precious metal electrodes or non-precious metal electrode end pieces.

[0004] The service life of spark plugs can be determined, for example, as the number of ignition cycles or the number of ignition sparks between the electrode ends or electrode end pieces until they become inoperable (no sparks). For rapid testing, spark test benches can be used, for example, in which only the electrode end piece to be tested or a temporary spark plug is installed. In the case of platinum spark plugs, typically between 35 and 45 million ignition sparks are generated using a standard automotive ignition coil, simulating a mileage of approximately 25,000 km for a vehicle with a four-cylinder engine. Extrapolated to a mileage of 100,000 km, this corresponds to 140 to 180 million ignition sparks.Alternatively, an engine test bench can be used to determine the service life at an average speed during 600 hours of continuous operation, or as a more meaningful test, a WLTP or NEDC test cycle can be completed on the engine test bench or on the vehicle. The term “electrode end piece” or “spark plug electrode end piece” used herein refers to the ends of spark plug electrodes. Ignition sparks are generated between the ends. Examples of such electrode end pieces include electrode rings, electrode caps and, in particular, electrode tips. Such electrode end pieces are firmly attached to spark plug electrodes, or more precisely to their ends, using methods known to those skilled in the art, such as welding. Examples of suitable welding methods include laser welding, resistance welding and arc welding. In the following, reference is made to an electrode end piece or “spark plug electrode end piece”.When we talk about a spark plug electrode end piece, this term can refer to a free, unattached electrode end piece as well as to an electrode end piece that is firmly attached to the electrode end.

[0005] A distinction is made here between spark plug electrodes that consist of a single material and spark plug electrodes to the end of which an electrode end piece made of a different material has been firmly attached.In other words, a distinction can be made, for example, between the following types of spark plugs: (i) spark plug with spark plug electrodes made of a single material, (ii) spark plug with a first spark plug electrode made of a single material and with a second spark plug electrode made of a single material, but different from that of the first spark plug electrode (a material different from the material of the first spark plug electrode), (iii) spark plug with a spark plug electrode made entirely of a single material and a spark plug electrode made of one material, to the end of which an electrode end piece made of a different material has been firmly attached, and (iv) spark plug with spark plug electrodes made of one material, to each end of which an electrode end piece made of a different material has been firmly attached.Designs in any combination are also possible; just one example is a combination of designs in the form of a spark plug with a spark plug electrode made entirely of a single material X and a spark plug electrode made of a material Y, to the end of which an electrode end piece made of a material X has been firmly attached. It goes without saying for the person skilled in the art that the ignition sparks are generated in the respective constellations between electrode ends, between electrode end and electrode end piece, or between electrode end pieces.

[0006] US 8,274,204 B2 discloses a spark plug for an internal combustion engine with one or more electrodes having an electrode material made of a platinum (Pt)-based alloy. The alloy comprises aluminum (Al) and one or more refractory metals selected from the group consisting of nickel (Ni), rhenium (Re), ruthenium (Ru), tantalum (Ta), molybdenum (Mo), and tungsten (W).

[0007] US 8,436,520 B2 discloses a spark plug for an internal combustion engine with a center electrode, a ground electrode, or both, containing an electrode material that is a platinum-based alloy. The electrode material may comprise, in addition to platinum (Pt), aluminum (Al) or silicon (Si), and at least one refractory element such as ruthenium (Ru), iridium (Ir), tungsten (W), molybdenum (Mo), rhenium (Re), tantalum (Ta), niobium (Nb), chromium (Cr), or a combination thereof.

[0008] A weakness of the conventional platinum spark plugs mentioned above is the occurrence of a so-called "balling effect" at the electrode end(s) or end pieces after extended periods of operation. This balling effect results in the formation of small balls containing a high platinum content or consisting essentially of platinum at the platinum electrode end(s). This results in the electrode gap being reduced to an unacceptable extent, leading to the formation of a short circuit between the electrode ends or the balls becoming detached and causing damage to the engine. Therefore, the objective was to prevent the occurrence of the balling effect or at least to significantly reduce it.

[0009] The applicant has discovered to its own surprise that the extent and speed of the development of the undesirable balling effect can be significantly reduced or its occurrence can even be prevented if electrodes or electrode end pieces of spark plugs made of a platinum alloy comprising a small proportion of 40 to 4700 ppm by weight (ppm by weight), preferably 40 to 4500 ppm by weight, in particular 40 to 4000 ppm by weight of at least one alloy metal selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr) are used or manufactured therefrom.

[0010] The solution to the problem or the invention therefore consists in the use of a platinum alloy comprising 40 to 4700 ppm by weight, preferably 40 to 4500 ppm by weight, in particular 40 to 4000 ppm by weight of at least one alloy metal M1 selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr) as material for or for producing at least one of the electrodes of a spark plug or for producing at least one electrode end piece of at least one of the electrodes of a spark plug.Calcium (Ca), scandium (Sc), yttrium (Y) and zirconium (Zr) are preferred alloying metals of type M1; within the group consisting of calcium (Ca), scandium (Sc), yttrium (Y) and zirconium (Zr) as preferred alloying metals of type M1, a further distinction is made below and in the patent claims between the metal zirconium (Zr) on the one hand and the metals calcium (Ca), scandium (Sc) and yttrium (Y) on the other hand as representatives of a subgroup of alloying metals of type M1 designated MT.

[0011] Preferably, the 40 to 4700 ppm by weight or the preferred 40 to 4500 ppm by weight or the particularly preferred 40 to 4000 ppm by weight of the at least one alloy metal M1 are composed of 40 to 4700 ppm by weight, preferably 40 to 4500 ppm by weight, in particular 40 to 4000 ppm by weight of zirconium (Zr) and / or of 40 to 400 ppm by weight of at least one alloy metal MT selected from the group consisting of calcium (Ca), scandium (Sc) and yttrium (Y), wherein the sum of the proportions of the alloy metals M1 does not exceed a total proportion of 4700 ppm by weight, preferably 4500 ppm by weight, in particular 4000 ppm by weight. In this respect, the use of a platinum alloy comprising 40 to 4700 ppm by weight, preferably 40 to 4500 ppm by weight, in particular 40 to 4000 ppm by weight of zirconium (Zr) and / or 40 to 400 ppm by weight is preferred.-ppm of at least one alloying metal M selected from the group consisting of calcium (Ca), scandium (Sc) and yttrium (Y), wherein the sum of the proportions of the alloying metals M1 does not exceed a total proportion of 4700 ppm by weight, preferably 4500 ppm by weight, in particular 4000 ppm by weight.

[0012] In addition to platinum and the at least one alloying metal of type M1, the platinum alloy usable according to the invention can also comprise one or more further alloying metals M2. The alloying metals M2 are the metals chromium (Cr), iron (Fe), gold (Au), iridium (Ir), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag), titanium (Ti), and tungsten (W). In other words, the platinum alloy usable according to the invention can be platinum (Pt) alloyed with 40 to 4700 ppm by weight, preferably 40 to 4500 ppm by weight, in particular 40 to 4000 ppm by weight of at least one alloy metal M1 selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr), and with 0 to 60 wt.% (wt. %), preferably 0.5 to 50 wt.-% of at least one alloy metal M2 selected from the group consisting of chromium (Cr), iron (Fe), gold (Au), iridium (Ir), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag), titanium (Ti) and tungsten (W). When reference is made herein to the group consisting of chromium (Cr), iron (Fe), gold (Au), iridium (Ir), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag), titanium (Ti) and tungsten (W), it is understood that iron (Fe), gold (Au), iridium (Ir), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag) and tungsten (W) are preferred alloying metals of type M2.

[0013] Iridium (Ir), molybdenum (Mo), palladium (Pd), rhenium (Re), ruthenium (Ru), and tungsten (W), as representatives of the M2 alloying metals, can increase the spark erosion resistance of the platinum alloy usable according to the invention. Chromium (Cr), gold (Au), and titanium (Ti), as representatives of the M2 alloying metals, can increase the oxidation resistance of the platinum alloy usable according to the invention. Copper (Cu) and silver (Ag), as representatives of the M2 alloying metals, can increase the electrical and thermal conductivity of the platinum alloy usable according to the invention. In particular, iron (Fe), cobalt (Co), copper (Cu), and nickel (Ni), as representatives of the M2 alloying metals, can have a price-dampening influence on the platinum alloy usable according to the invention.

[0014] In addition to platinum and the aforementioned alloy metals M1 and optionally M2, the platinum alloy usable according to the invention can also comprise other elements different from these, which may have inadvertently entered the platinum alloy due to technical circumstances, e.g., as a result of unintentional but unavoidable incorporation during the production of the platinum alloy. In other words, such other elements can be present in the platinum alloy usable according to the invention as unavoidable impurities, and if applicable, only in very small proportions of, in individual cases, e.g., >0 to generally <100 ppm by weight. In any case, such unavoidable impurities are not intentionally added or introduced into the platinum alloy usable according to the invention.For example, the platinum alloy usable according to the invention may be "contaminated" by oxygen, in particular by oxidic oxygen; the oxygen content in the platinum alloy usable according to the invention may then be, for example, in the range of 3 to 15 ppm by weight, preferably below 10 ppm by weight.

[0015] If unavoidable impurities are present, which is generally the case, the total proportion of unavoidable impurities within the platinum alloy that can be used according to the invention in the form of elements other than platinum and the alloying metals M1 and M2 is >0 to <1000 ppm by weight. In a first embodiment, the platinum alloy that can be used according to the invention can consist of platinum (Pt), 40 to 4700 ppm by weight, preferably 40 to 4500 ppm by weight, in particular 40 to 4000 ppm by weight of at least one alloying metal M1 selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr), 0 to 60% by weight, preferably 0.5 to 50% by weight.-% of at least one alloying metal M2 selected from the group consisting of chromium (Cr), iron (Fe), gold (Au), iridium (Ir), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag), titanium (Ti) and tungsten (W), and 0 or >0 to <1000 ppm by weight of unavoidable impurities in the form of one or more elements other than platinum and the alloying metals M1 and M2.

[0016] In a second and preferred embodiment, the platinum alloy usable according to the invention can consist of platinum (Pt), 40 to 4700 ppm by weight, preferably 40 to 4500 ppm by weight, in particular 40 to 4000 ppm by weight of at least one alloy metal M1 selected from the group consisting of calcium (Ca), scandium (Sc), yttrium (Y) and zirconium (Zr), 0 to 60% by weight, preferably 0.5 to 50% by weight of at least one alloy metal M2 selected from the group consisting of chromium (Cr), iron (Fe), gold (Au), iridium (Ir), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag), titanium (Ti) and tungsten (W), and 0 or >0 to <1000 ppm by weight of unavoidable impurities in the form of a or more elements other than platinum and the alloying metals M1 and M2.

[0017] In a third and particularly preferred embodiment, the platinum alloy usable according to the invention can consist of platinum (Pt), 40 to 4700 ppm by weight, preferably 40 to 4500 ppm by weight, in particular 40 to 4000 ppm by weight of zirconium (Zr) and / or 40 to 400 ppm by weight of at least one alloying metal MT selected from the group consisting of calcium (Ca), scandium (Sc) and yttrium (Y), 0 to 60% by weight, preferably 0.5 to 50% by weight of at least one alloying metal M2 selected from the group consisting of chromium (Cr), iron (Fe), gold (Au), iridium (Ir), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag), titanium (Ti) and tungsten (W), and 0 or >0 to <1000 ppm by weight of unavoidable impurities in the form of one or more elements other than platinum and the alloying metals M1 and M2, the sum of the proportions of the alloying metals M1 having a total proportion of 4700 ppm by weight, preferably 4500 ppm by weight.-ppm, in particular 4000 wt. ppm. Examples of expedient embodiments of platinum alloys which can be used according to the invention include those of the type PtNi10-30 (alloy of platinum with a proportion of 10 to 30 wt. % nickel), PtNi>30-40, Ptlr1-10 (preferably Ptlr1-5), PtRu1-10 (preferably PtRu1-5) and Ptl r1-5Ni 1-5, each alloyed with 40 to 4700 wt. ppm, preferably 40 to 4500 wt. ppm, in particular 40 to 4000 wt. ppm of at least one alloy metal M1 selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr). In addition to the elements explicitly mentioned in this paragraph, these embodiments may also comprise other elements different from them which may have inadvertently entered the platinum alloy due to technical circumstances, e.g. as a result of unintentional but unavoidable incorporation during the manufacture of the platinum alloy.In other words, such additional elements may be present as unavoidable impurities, and if applicable, only in very small amounts, ranging from, for example, >0 to generally <100 ppm by weight in individual cases. In any case, such unavoidable impurities are not intentionally added or introduced. The total amount of such unavoidable impurities is 0 or >0 to <1000 ppm by weight.

[0018] Examples of further expedient and preferred embodiments of platinum alloys which can be used according to the invention include those of the type PtNi 10-30, PtNi>30-40, Ptrl1-10 (preferably Ptrl1-5), PtRu1-10 (preferably PtRu1-5) and Ptrl1-5Ni1-5, each alloyed with 40 to 4700 ppm by weight, preferably 40 to 4500 ppm by weight, in particular 40 to 4000 ppm by weight of zirconium (Zr) and / or with 40 to 400 ppm by weight of at least one alloying metal MT selected from the group consisting of calcium (Ca), scandium (Sc) and yttrium (Y), wherein the sum of the proportions of the alloying metals M1 has a total proportion of 4700 ppm by weight, preferably 4500 ppm by weight, in particular 4000 ppm by weight. Regarding other elements and unavoidable impurities, the same applies as already stated in the examples of suitable embodiments.

[0019] To avoid any misunderstandings, the platinum, the alloying metal(s) of type M1 comprised by the platinum alloy usable according to the invention, as well as the alloying metal(s) of type M2 comprised by the platinum alloy usable according to the invention, optionally but preferably, are present in elemental form in the oxidation state 0 in the platinum alloy. The platinum alloy usable according to the invention is not a platinum alloy dispersion-hardened by oxidation, such as the platinum DPH products available from Heraeus; rather, the platinum alloy usable according to the invention is a platinum alloy dispersion-hardenable by oxidation. In the inventive use in question here, however, no dispersion hardening of entire said electrodes or entire said electrode end pieces takes place, i.e.neither during their manufacture nor during the manufacture of a spark plug equipped with them nor during the operation of such a spark plug.

[0020] The platinum alloy usable according to the invention can be produced by conventional methods known to those skilled in the art, e.g. by melting together the elements forming the platinum alloy, i.e. the platinum, the at least one alloying metal M1 and optionally the at least one alloying metal M2. It is possible to use an induction furnace, a plasma furnace or an arc furnace, and work can be carried out under vacuum or in a protective gas atmosphere. The materials used, for example in the form of metals and / or master alloys, can have a purity of e.g. >99.8 wt.%. The molten platinum alloy is typically poured into a mold at room temperature, where it cools and solidifies.The solidified platinum alloy can then be processed into tubes, sheets, or wires using conventional forming processes known to those skilled in the art, such as forging, rolling, tube or wire drawing. These tubes, sheets, or wires can then be further processed into said spark plug electrodes, spark plug electrode end pieces, or spark plugs using conventional manufacturing processes known to those skilled in the art. Examples of manufacturing steps within such manufacturing processes include sawing, shearing, punching, extrusion, and welding. The platinum alloy usable according to the invention can also be processed into finished semi-finished products, such as tubes, sheets, strips, or wires, by direct casting.

[0021] As demonstrated by ignition spark tests on an ignition spark test bench mentioned above, spark plug electrodes or spark plug electrode end pieces manufactured using the platinum alloy are characterized by an exceptionally long service life during the operation of spark plugs equipped with them, for example in the range of 200 to 250 million ignition cycles (corresponding to approximately 150,000 km of mileage for a vehicle with a four-cylinder engine) compared to the already long service life of conventional platinum spark plugs of the state of the art of 140 to 180 million ignition cycles (corresponding to approximately 100,000 km of mileage for a vehicle with a four-cylinder engine). It has been shown that the proportion of 40 to 4,700 ppm by weight, preferably 40 to 4,500 ppm by weight, in particular 40 to 4,000 ppm by weight-ppm of the at least one alloy metal M1 selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr) in the platinum alloy usable according to the invention can lead to a significant reduction in the undesirable balling effect mentioned above during engine operation. Without wishing to be bound to a particular theory, it is merely assumed that the surface tension of the molten electrode material made of the platinum alloy usable according to the invention changes under the ignition spark. Molten material has a liquid flow due to the plasma pressure of the ignition spark; it can be assumed that this liquid flow may be reversed and, as a result, no more material builds up in front of the ignition spark, but is distributed flatly behind the ignition spark.

[0022] The invention also relates to the following products or articles, each of which can be produced using any of the aforementioned embodiments of the platinum alloy: a spark plug electrode made of any of the aforementioned embodiments of the platinum alloy usable according to the invention, a spark plug electrode end piece made of any of the aforementioned embodiments of the platinum alloy usable according to the invention, a spark plug comprising at least one electrode made of any of the aforementioned embodiments of the platinum alloy usable according to the invention, and a spark plug comprising at least one electrode end piece made of any of the aforementioned embodiments of the platinum alloy usable according to the invention. It was pointed out at the outset that the term “electrode end piece orSpark plug electrode end piece" can refer to an electrode end piece that is firmly bonded to a spark plug electrode end, for example by welding. In this respect, in connection with the products or objects mentioned here - insofar as they concern or comprise such a firmly bonded spark plug electrode end piece - it should be pointed out for the sake of completeness that the ">0 to <1000 ppm by weight of unavoidable impurities" repeatedly mentioned here can enter or have entered the platinum alloy forming the spark plug electrode end piece not only during the production of a respective platinum alloy but possibly also as a result of unintentional incorporation during the firm bonding, for example from a welding filler material used during a welding process.

Claims

Patent claims 1. Use of a platinum alloy as a material for or for producing a spark plug electrode or a spark plug electrode end piece or at least one of the electrodes of a spark plug or at least one electrode end piece of at least one of the electrodes of a spark plug, wherein the platinum alloy consists of platinum (Pt), 40 to 4700 wt. ppm of at least one alloy metal M1 selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr), 0 to 60 wt. % of at least one alloy metal M2 selected from the group consisting of chromium (Cr), iron (Fe), gold (Au), iridium (Ir), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag), titanium (Ti) and tungsten (W), and 0 or >0 to <1000 wt. ppm of unavoidable Impurities in the form of one or more elements other than platinum and the alloying metals M1 and M2.

2. Use according to claim 1, wherein the alloying metal M1 is selected from the group consisting of calcium (Ca), scandium (Sc), yttrium (Y) and zirconium (Zr).

3. Use according to claim 1, wherein the 40 to 4700 ppm by weight of the at least one alloy metal M1 are composed of 40 to 4700 ppm by weight of zirconium (Zr) and / or of 40 to 400 ppm by weight of at least one alloy metal MT selected from the group consisting of calcium (Ca), scandium (Sc) and yttrium (Y), wherein the sum of the proportions of the alloy metals M1 does not exceed a total proportion of 4700 ppm by weight.

4. Use according to claim 1, wherein the platinum alloy is selected from those of the type PtNi 10-30, PtNi>30-40, Ptrl1-10, PtRu1-10 and Ptrl1-5Ni1-5, each alloyed with 40 to 4700 ppm by weight of at least one alloy metal M1 selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr), wherein the platinum alloy comprises a total proportion of 0 or >0 to <1000 ppm by weight of unavoidable impurities in the form of further elements other than those explicitly mentioned in the present claim.

5. Article selected from the group consisting of spark plug electrodes made of a platinum alloy, spark plug electrode end pieces made of a platinum alloy, spark plugs comprising at least one electrode made of a platinum alloy and spark plugs comprising at least one electrode end piece made of a platinum alloy, wherein the platinum alloy consists of platinum (Pt), 40 to 4700 ppm by weight of at least one alloy metal M1 selected from the Group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr), 0 to 60 wt.% of at least one alloying metal M2 selected from the group consisting of chromium (Cr), iron (Fe), gold (Au), iridium (Ir), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), palladium (Pd), rhenium (Re), ruthenium (Ru), silver (Ag), titanium (Ti) and tungsten (W), and 0 or >0 to <1000 wt. ppm of unavoidable impurities in the form of one or more elements other than platinum and the alloying metals M1 and M2.

6. The article of claim 5, wherein the alloying metal M1 is selected from the group consisting of calcium (Ca), scandium (Sc), yttrium (Y) and zirconium (Zr).

7. Article according to claim 5, wherein the 40 to 4700 ppm by weight of at least one alloying metal M1 are composed of 40 to 4700 ppm by weight of zirconium (Zr) and / or of 40 to 400 ppm by weight of at least one alloying metal MT selected from the group consisting of calcium (Ca), scandium (Sc) and yttrium (Y), wherein the sum of the proportions of the alloying metals M1 does not exceed a total proportion of 4700 ppm by weight.

8. Article according to claim 5, wherein the platinum alloy is selected from those of the type PtNi 10-30, PtNi>30-40, Ptrl1-10, PtRu1-10 and Ptrl1-5Ni1-5, each alloyed with 40 to 4700 wt. ppm of at least one alloying metal M1 selected from the group consisting of calcium (Ca), germanium (Ge), lanthanum (La), scandium (Sc), yttrium (Y) and zirconium (Zr), wherein the platinum alloy comprises a total proportion of 0 or >0 to <1000 wt. ppm of unavoidable impurities in the form of further elements other than those explicitly mentioned in the present claim.